64491881 has 2 divisors, whose sum is σ = 64491882. Its totient is φ = 64491880.

The previous prime is 64491877. The next prime is 64491883. The reversal of 64491881 is 18819446.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 46717225 + 17774656 = 6835^2 + 4216^2 .

It is a cyclic number.

It is not a de Polignac number, because 64491881 - 2² = 64491877 is a prime.

It is a super-2 number, since 2×64491881² = 8318405429836322, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 64491883, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (64491883) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 32245940 + 32245941.

It is an arithmetic number, because the mean of its divisors is an integer number (32245941).

Almost surely, 2^64491881 is an apocalyptic number.

It is an amenable number.

64491881 is a deficient number, since it is larger than the sum of its proper divisors (1).

64491881 is an equidigital number, since it uses as much as digits as its factorization.

64491881 is an evil number, because the sum of its binary digits is even.

The product of its digits is 55296, while the sum is 41.

The square root of 64491881 is about 8030.6837193355. The cubic root of 64491881 is about 401.0221379436.

The spelling of 64491881 in words is "sixty-four million, four hundred ninety-one thousand, eight hundred eighty-one".